Tfi 470 

.H73 

Copy 1 ihject to Bevision, 



H73 




[TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.] 

THJS STBENGTH OF WBOUGHT IBON AS AFFECTED BT 
ITS C031P0SITpN AND BY ITS BEDUCTION IN 
/ BOLLING. 

BY A. L. HOLLEY, PH.B., M.I.C.E., NEW YORK- CITl^O.^ 

(■Read at the Philadelphia Meeting, February, 1878. ) ^>«^-- - '^^"i.--<^ 



^^ 



w ^ This paper is an abstract and a discussion of results obtained by 
^ i the United States Test Board in experiments upon 14 brands of 
wrought iron, most of which are well known and of high repute.* 
The iron was all intended for chain-cables ; it was tested in the form 
of bars, usually of nine sizes, from 1 inch to 2 inches round, and also 
in the forms of single links and short chains. Not less than 2000 
tensile tests were made, each showing elastic limit, elongation, and 
reduction of area. This work was done with conspicuous intelli- 
gence and fidelity, at the Washington Navy Yard, by Commander 
L. A. Beardslee. Some important practical results and principles 
which he has developed, and others which he has confirmed, will be 
referred to. The chemical part of this work consists of 42 com- 
plete analyses (including slag), by Mr. Blair, chemist to the Board. 

EFFECTS OF COMPOSITION ON STRENGTH. 

Variations in the physical qualities of iron may be due to different 
composition, or to different treatment in manufacture, or to both 
these complex causes. In order to determine the specific causes of 
variation, one class of altering conditions should be made to vary 
largely, while the other classes should be kept uniform. Then 
another class should be varied, and so on, until the value of each is 
ascertained. As all the irons under consideration were intended to 
have that purity and refinement which was deemed indispensable in 
chain-cables, their chemical analyses are perhaps more important in 
proving that physical variations result chiefly from treatuient, than 
in pointing out the specific effects of certain ingredients. While 
the subject of treatment — especially the increase of strength by 
greater reduction in rolling — may be the more important one, it can 
be best appreciated after we havefamiliarized ourselves with the gen- 
eral chemical and physical characters of the irons. Th^ typical 
facts are given in the following tables. 



* As the present object of the Board is not to compare the products of different 
makers, but to discover the physical effects of various composition and treatment, 
the irons are designated by letters rather than by their trade name?. 



f 



THE STRENGTH OF WROUGHT IRON. 



Table I. Analyses of Irons Used in Making Chain Cables. 









A 2 

Bl 7-16 

CI34 

D 1 

D 2 

Dli^,lotl 

D13^, lot2 

D2, Nov. '76 

Eli/^ 

F 1% 

Fxli/g, lot 1 

Fxl, lot 2 

Fx%lot3 

Jl 7-16 

Jl% 

Jl 11-16 

Jl% 

J 13^ 

K 

K \% 

LIV^ 

LI 7-16 

L 1% 

LI 11-16 

LI 13-16... -.. 

h%.. 

L>^ 

MIK 

Ml% 

Ml% 

Mli^ 

Ml% 

M 13^, weld end 
M 11^, butt end 
M 1%, weld end. 
M 1%, butt end 

Nli/g 

N2 

O 1 

O 1% 

P 1....... 

P 1^ 



1 

1 

1 




-5 





1 
1 


i 

a 
1 


I 
6 


Cobalt. 


0.007 


0.178 


0.139 


0.021 


0.031 


0.172 


0.068 ' 


0.008 


0.231 


0.156 


0.015 


0.017 


0.038 


0.047 


! 0.007 


0.169 


0.154 


0.042 


0.021 


0.046 


0.029 


0.005 


0.239 


0.171 


0.028 


0.029 


0.008 


0.023 


1 0.009 


0.191 


' 0.185 


0.045 


0.097 


0.012 


0.023 


; 0.005 


0.118 


0.135 


0.020 


0.071 


0.016 


0.023 , 


0.005 


0.158 


0.108 


0.024 


0.038 


0.018 


0.031 


0.005 


0.213 


0.163 


0.035 


0.021 


0.007 


0.023 1 


0.013 


0.181 


0.159 


0.018 


0.021 


0.054 


0.044 


0.004 


0.201 


0.158 


0.026 


0.048 


0.002 


0.018 , 


0.004 


0.187 


0.163 


0.032 


0.031 


0.010 


0.026 j 


0.004 


0.197 


0.170 


0.033 


0.045 


0.008 


0.037 1 


0.004 


0.193 


0.170 


0.028 


0.039 


0.006 


0.042 


, 0.003 


0.140 


0.182 


0.027 


Trace. 


0.004 


Trace. 


i 0.005 


0.291 


0.321 


0.034 


0.029 


0.011 


0.013 


0.005 


0.223 


0.295 


0.035 


0.029 


0.009 


0.003 j 


0.003 


0.213 


0.303 


0.051 


0.007 


0.011 


0.013 


0.004 


0.154 


0.257 


0.033 


0.053 


Trace. 


Trace. ' 


0.005 


0.161 


0.156 


0.062 


0.018 


0.048 


0.016 


0.006 


0.134 


0.143 


0.071 


0.021 


0.046 


0.013 


Trace. 


0.065 


0.105 


0.453 


0.006 


0.008 


Trace. 1 


Trace. 


0.073 


0.098 


0.328 


0.005 


0.008 


0.013 


Trace. 


0.067 


0.098 


0.512 


0.029 


0.010 


0.010 


Trace. 


0.074 


0.080 


0.212 


0.014 


0.006 


0.010 


Trace. 


0.084 


0.093 


0.248 


0.016 


0.008 


0.008 1 


0.001 


0.089 


0.103 


0.229 


0.019 


0.007 


0.015 


0.004 


0.232 


0.175 


0.042 


0.040 


0.006 


0.026 


1 0.005 


0.248 


0.174 


0.026 


Trace. 


0.314 


0.110 


0.015 


0.233 


0.204 


0.034 


0.059 


0.370 


0.058 


0.007 


0.317 


0.259 


0.039 


0.021 


0.374 


0.098 


0.008 


0.219 


0.159 


0.063 


0.022 


0.328 


0.052 


0.010 


0.221 


0.164 


0.064 


0.031 


0.340 


0.053 


0.005 


0.211 


0.182 


0.055 


Trace. 


0.324 


0.104 


0.006 


0.209 


0.203 


0.055 


Trace. 


0.322 


0.097 


1 0.008 


0.263 


0.177 


0.034 


Trace. 


0.430 


0.090 


0.007 


0.269 


0.261 


0.028 


Trace. 


0.422 


0.087 


0.004 


0.190 


0.159 


0.055 


0.026 


0.036 


0.026 


0.006 


0.192 


0.169 


0.028 


0.050 


0.028 


0.031 


0.004 


0.067 


0.065 


0.045 


0.007 


0.046 


0.033 


0.005 


0.078 


0.073 


0.042 


0.005 


0.046 


0.034 


0.009 


0.250 


0.182 


0.033 


0.033 


0.081 


0.037 


0.001 


0.095 


0.028 


0.066 


0.009 


0.008 


0.020 



0.078 
0.037 


1.210 


0.031 




0.028 
0.026 
0.029 


0.570 
0.546 


0.026 




0.028 
0.042 


0.874 


0.028 
0.013 


0.650 


0.037 




0.042 





0.008 
0.013 
0.008 
0.008 
0.013 
0.049 
0.037 
0.011 
0.013 
0.016 
0.013 
0.018 
0.018 
0.026 
0.340 
0.029 
0.175 
0.039 
0.0.34 
0.246 
0.243 
0.313 
0.303 
0.018 
0.028 
0.034 
0.037 
0.057 
0.023 



1.120 
1.026 
0.678 
1.230 
1.724 
0.540 
0.354 
0.326 
0.192 
0.308 
0.452 
0.376 
0.388 
0.668 
1.096 
0.884 
1.034 
0.674 
0.828 
0.994 
1.078 
1.382 
1.738 
1.258 
2.262 
1.168 
0.974 
0.848 
1.214 



07 



PROPORTION OF TENACITY OF SINGLE LINKS TO 
I TENACITY OP BARS. 



51, 



50, 
54, 

52, 
53, 

51, 

49, 

50, 

50, 



53 

53,|l 

50; 
53, 
53, 

57, 
60, 

57,) 
55, 
50, 

52, 
54,1 



1 \ 



172.5 



.76.5 



178.2 
176.3 



. . 168.9 
. . 163. 



!160 



n Hz 



168.4 



173 6 
181. 

169.1 
175.8 



172.9 



185.4 
160 5 



178. 



163.1 



160. 



If 



170.8 



163.4 

175.7 

170.2 
176.2 



159.3 



149.9 
152.7 



177.2 

178. 



185.6 



179.6 



187.8 
179.2 
123.4 



H 



172. 



191.4 
172.9 

193.4 



186. 
164. 

166. 



174.4 



183.4 



174.6 

163.5 

156 6 

171.1 
166 8 



165. 



189.6 
166.4 

179.2 



187.7 
175.1 

175 8 



183.2 



188. 



109.6 

166.7 

116.2 

137.3 
169.6 



180.1 
177.6 



183.2 



171. 



174.8 



174. 



199. 
175.8 

182.6 



178.4 
182.2 

172.4 



174. 



176.4 



173.8 



174.1;173.4 

180. il75.6 

162.1 1 154.9 



169. 
172.8 



180.9 



172. 



179. 



167.6 

163.2 
158. 



155. 



160. 



164 



181. 



172. 



162.1 



AVEK- 
AGES. 



173.3 



175.4 



183.1 
171.7 



178.5 



183.6 
168.9 

169.6 



175.7 

182.6 

162.6 

168.7 

152. 

160.9 
161.8 



169.2 



BSTRACT OF PHYSICAL TESTS OF 
Ion of Bars, and Proportion of Strength of 



CHAIN IRONS. 
Bar IDeveloped in Single Links and in Slinrt Cliains. 



53,109; 42 4 20. 



50,39.5 
5.3,800 
53,264 



24.5 50,307 i', 

15.7J . . . ! , 

21.61 ... ; . 
28.4 

21.5 
23.4 



20.3 1 
20.3 
26.5 
48.9 



1.1 .56,201' 47.5 



51,037 
47,478 



21.51 20.4 
54.8J 24. 



.52.9| 
51,762 49 sl 27.7 



47,872 
60,763 



.51,748; 1.3. 
48.24fl 51. 



51,754 

58,050 

66,598 

55,683 
56,421 

54,329 

51.134 



49,872 49. | 24. 

I I 



.54,363 
.54,270 



49. 22.2 
36.1 17.2 
40.6 15.4 



18. 



45.81 27.7 
21.9 



155.3 
155 8 



155.5 
153.5 

163.9 



PROPORTION OF TENACITY OF SINGLE LINKS TO 
TENACITY OP BARS. 



1 IJ l.t 1/5 If l./j H l| m \i ]|3. i| 2 



182.6 
162.6 



itted from averages, they breaking at welds 



THE STRENGTH OF WROUGHT IRON. 



Table III. Relative Values of Irons in Bars in tenacity, red. of 
area amd elon., and in Proportion of Chain to Bar. 

















Proportion of 




Order 


Tensile strength. 


Reduction of 
area. 


Elongation. 


tenacity of short 
chain to that of 


Order 


I of 
' value. 














bar. 


of 
value. 


Iron. 


Lbs. per 
sq. inch. 


Iron. 


Per 
cent. 


Iron. 


Per 

cent. 


Iron. 


Per ct. 


1 


L 


66,598 





54.2 


Px 


29.9 


B 


168.2 


1 


2 


K 


58,050 


A 


49.0 


E2 


27.7 


A 


168.1 


2 


3 


D2 


56,673 


Px 


48.9 


P 


23.2 





165.7 


3 


4 


C2 


56,001 


F 


48.1 





22.7 


Px 


163.9 


4 


5 


M 


55,683 


rn 


47.8 


A 


22.2 


F 


163.2 


5 


6 


P 


54,363 


P 


46.6 


Fx2 


22.0 


D2 


1583 


6 


7 


N • 


54,329 


Fx2 


46.2 


F 


21.9 


Fx 3 


157.5 


/ 


8 


Fxl 


54,271 


E2 


45.8 


Fxl 


21.8 


C2 


156.8 


8 


9 


Px 


54,270 


Fxl 


45.3 


M 


21.0 


N 


155.8 


9 


10 


Dl 


53,292 


El 


45.0 


D2 


20.9 


P 


154.5 


10 


11 


Fx2 


53,107 


D2 


43.8 


N 


20.2 


Fxl 


151.4 


11 


12 


B 


52,764 


CI 


40.6 


Dl 


18.2 


M 


150.7 


12 


13 


A 


52,579 


M 


38.2 


C2 


18.0 


K 


141.6 


13 


14 


El 


52,533 


C2 


38.1 


K 


17.9 








15 


E2 


52,471 


K 


38.0 


B 


17.2 








16 


J 


51,754 


B 


36.1 


CI 


15.4 








17 


F 


51,192 


N 


33.0 


El 


15.3 








18 





.51,134 


L 


30.4 


J 


12.6 








19 


CI 


50,765 


J 


25.9 


L 


8.3 









Table IV. Relative Values of Irons. Average for Bars, Short Chains, 

and Single Links. 



Order of value. 



Tenacity 

I Reduction of area . 

Elongation 

I Welding value*.... 

j Resilience 



l| 2 


3 


4 


K D2 


C2 


M 


A 


Px 


F 


Pxl P 





A 


B 1 A 





Px 


A 1 Fx3 


Fx2 


F 




p !n 

i 

P I Fx? 
Fx3 i F 
F ' D2 

I D2 



Px 

Fxl 

D2 

Fxl 

Fx3 

P 

C2 



Fxl 

M 

C 



Fx3l B 



M 02 ; K 
D2 N C2 

N I P Fxl 

'Px ! M 

IB 1 



12 



Table I. Analyses of the irons. 

. Table II. Abstracts of physical tests of irons, and proportions of 
strength of links to that of bars. 

Table III. Relative values of irons in bars, in tenacity, reduction 
of area, and elongation, and in proportion of chain to bar. 

Table IV. Relative values of irons. Average for bars, short 
chains, and single links. 

Table V. Showing efiects of variation of reduction and of uni- 
formity of reduction on strength. 



* Iron L, bars of which exceeded all others in tenacity, when tested in single 
links only, gave the lowest welding value. 



f 



4 THE STRENGTH OF WROUGHT IRON. 

In the Report of the Board, under the head of Phosphorus, the 
leading chemical and physical facts about each iron likely to be 
affected by this element are compared, and then the group of irons 
is considered, and a conclusion is reached ; under the head of Silicon 
the irons are again gone over in a similar manner, and so on with 
Carbon and other ingredients. A description of a few irons in which 
composition should have the greatest influence on strength will suf- 
fice to introduce these conclusions.* 

Effects of Phosphorus. 

Iron 0. P., 0.07, Si., 0.07, C, 0.04. Slag medium. 

Chemical impurities all very low. 

The iron had been thoroughly worked. 

Tenacity as bar and as link very low. 

Ductility as bar and as link very high. 

Welds very good. 

Low phosphorus does not alone account for these qualities. Iron 
F with P., 0.20, Si., 0.16, and C, 0.03, has about the same tenacity 
and welding power, and approaches the same ductility. Iron P 
with P., 0.17, Si., 0.10, and C, 0.05, has about equal ductility. See- 
ing that the thorough working of the small bars decreased welding- 
power, as compared with that of the less compressed large bars, it 
is probable that method of manufacture is an important factor in all 
physical results. The effects of low phosphorus are not conspicuous. 

Iron P., P., 0.17, Si., 0.10, C, 0.05. Slag very low. 

P., and C, medium ; other impurities rather low. 
. Tenacity high as. link and as bar. 

Ductility high as link and as bar. 

Welding power medium. 

Iron properly worked for tenacity and durability, but overworked 
for welding. (See iron Px.) 

. This iron had the highest average of good qualities, and was the 
best for general constructive purposes. The characteristic effects of 
phosphorus are shown by the behavior of two specimens of iron 
P, viz. : 

1 in. bar. P., 0.25, had tenacity 58,000 lbs., and elongation 14 
per cent. 

•^ It is hoped that those who are interested in this subject will analyze these 
data, and point out new readings and missing links in the evidence, if such there 
may be. 



THE STRENGTH OF WROUGHT IRON. 5 

If ill. bar, P., 0.09, had tenacity 53,000 lbs., and elongation 24 
per cent. 

But this increased tenacity and decreased ductility of the 1 in. bar 
are not due to P. alone; it had Si. 0.18 against Si. 0.03 in the 
larger bar, and it had more reduction in rolling. Phosphorus 0.17 
may thus accompany the highest general value ; that this element 
did not cause inferior welding, may be inferred from the fact that 
iron Px, made of the same materials and in the same way, except 
that one course of piling and hammering was omitted, welded much 
better, although its tenacity and ductility were decreased. 

Iron D, P., 0.18 (0.12 to 0,24); Si., 0.15; C, 0.03; slag low. 

Carbon low; other impurities medium. 

Different bars very differently worked. 

Tenacity high as bar and link. 

Ductility below medium as bar and link. 

Welds very good. 

There are various proofs that low phosphorus, even with low 
silicon, do not make high ductility, and that the amount of reduc- 
tion is the more important factor. For instance : 

1 in. bar, P., 0.24, Si., 0.17, has tenacity 61,000 lbs. ; elongation, 26 per cent. 
1^ in. bar, P., 0.16, Si., 0.11, has tenacity 56,000 lbs.; elongation, 23 per cent. 
2. in. bar. P., 0.19, Si,, 0.18, has tenacity 51,000 lbs. ; elongation, 18 per cent. 



The welds of the medium-sized and worked bars were best, but 
all were good. No harmful effect of phosphorus can be traced in 
this iron. 

Iron B welded best, and had P., 0.23, and C, 0.015. 

IronF. P., 0.20; Si,, 0.16; C, 0.03; slag low. 

Carbon low; other impurities medium. 

Iron suitably worked for welding, and very uniform. 

Tenacity as bar and as link very low. 

Ductility high. 

Welding power good. 

The remarkable uniformity of this iron proves it to have been 
made with great care from selected materials. Why its tenacity 
is so low it is difficult to say on chemical grounds. The same iron, 
Fx, more worked, gives a medium tenacity, with substantially the 
same analysis. Iron A, with less P,, Si,, and C, is stronger. 
Iron E has lower P., the same Si., and only 0,02 C, and yet a 
higher tenacity. 



Q THE STRENGTH OF WROUGHT IRON, 

: Iron Fx (F more worked). P., 0.19; Si., 0.17; C, 0.03. 
Ingredients substantially the same as in F. 
Iron much more worked than F. 
Tenacity medium in link and bar. 
Ductility good. 
Welding power below medium. 

Iron B, P., 0.23; Si., 0.16; C, 0.015. 

P. rather high; Si. medium; and C. very low. 
■ Iron not sufficiently worked for strength. 

Tenacity rather low. 

Ductility quite low. 

Welds very good. 

Notwithstanding the extremely low C, the iron was not ductile. 
P. may well account for this, but not for low tenacity, as some of 
iron P had more P. and much higher tenacity. Low C. may partly 
account for low tenacity and good welds, but small reduction seems 
to be an equal cause. High P. did not prevent excellent welding. 

Iron M, P., 0.25 (0.21 to 0.32); Si., 0.20 (0.16 to 0.26); C, 
0.04; Ni., 0.18 (0.03 to 0.34); Cu., 0.34 (0.13 to 0.43); slag various. 

P. rather high; Si. above medium; copper and nickel high; 
C/ rather low. 

The amount of work the iron received can only be inferred from 
the sizes of the bars. 

Tenacity considerably above average.. 

Ductility average. 

Welds weak. 

The character of this iron is so complex, and its physical character 
varies so much in the same sized bars, that no satisfactory analysis 
of the data can be made. It seems certain, from a comparison of 
the tables, that neither copper, nickel, cobalt, nor slag materially 
affected strenofth ; the effects of these ingredients on welding will be 
considered under another head."^ 

Conclusions about Phosphorus. — The best of these irons average : 
P., 0.15 to 0.20. The extreme limits are 0.065 and 0.317. A soft 

* ChTomium occurs only in iron M, four analyses of which show Cr. 0.061 to 
0.089. As this element is known to increase the tenacity of steel, it may have 
brought iron M, up to a good standard of tenacity, without helping its other 
structural qualities. These experiments give no absolute evidence as to the ef- 
fects of chromium ; but it may be said that when mere tenacity is made the cri- 
terion of fitness, an untrustworthy iron like M, may be '' physicked " in various 
ways to meet thai requirement. 



THE STRENGTH OF WROUGHT IRON. 7 

boiler-plate steel might have the former amount ; the latter would 
give high tenacity and brittleriess to even a low-carbon steel. The. 
investio-ations have been made so difficult by the chemical similarity 
and general purity of most of the irons, and by their various degrees 
of reduction in rolling, that the effect of phosphorus cannot be 
independently traced. While special bars having chemical and 
structural conditions otherwise similar, seem to be increased in 
tenacity and brittleness by high phosphorus, other bars low in thi^ 
element are not the mildest. Of one iron, a 1 in. bar, with P. 0.25, 
had 5000 lbs. more tenacity per square inch and 10 per cent, less 
stretch than a If in. bar with P. 0.09. But the 1 in. bar had also 
silicon 0.18, while the If in. had Si. 0.03; and the smaller bar 
received greater reduction and strength in rolling, as we shall see 
•farther on. 

The phosphorus (average in each iron) in the irons likely to be 
aifected by it, runs very irregularly as follows, beginning with the 
highest of the following physical values : Tenacity^ P., 0.18, 0.17, 
0.25, 0.17, 0.19, 0.19, 0.20, 0.18, 0.20, 0.07. Reduction of area, P., 
0.07, 0.18, 0.20, 0.19, 0.18, 0.20, 0.19, 0.16, 0.17, 0.25, 0.23, 0.19: 
Elongation, P., 0.18, 0.07, 0.18, 0.20, 0.20, 0.19, 0.25, 0.16, 0.19, 
0.17, 0.23. 

It may be generally stated that phosphorus 0.20, with carbon 
about 0.03 and silicon under 0.15, gave the best chain cable irons 
of this group, although low tenacity and high ductility are the chief 
requirements of such irons. 

The effects of the different constituents on welding will be con- 
sidered under that head. 

Effects of Silicon. 

See foregoing descriptions of irons 0, P, F, and M. 

In iron F, w^iich is among the highest in silicon, did this element 
cause the very low tenacity despite the fair amount of P. (0.20)? 
If so. Si. must affect tenacity more than it affects ductility. But 
this is not the fact. In iron J ductility as well as tenacity is 
reduced very low by high Si. (0.27). 

Iron J, Si., 0.27 (0.18 to 0.32); P., 0.20; C, 0.035. Slag average. 

Silicon high; other impurities medium. 

Iron not overworked. 

Tenacity very low in bar and link. 

Ductility very low in bar and link. 

Weld rather bad. 



8 THE STRENGTH OF WROUGHT IRON. 

There was no apparent chemical or physical cause for this low 
strength, except excessive silicon. Under sledge blows the bars 
split as often as they broke off, and the faces of the fracture were 
like layers of charcoal, although both carbon and slag were medium. 

Conclusions about Silicon. 
No ingredient of steel is less understood than this one. The techni- 
cal managers of the Terrenoire Works in France, who have been nota- 
bly successful in their steel manufactures founded on chemical induc- 
tion, especially in the manufacture of sound steel castings which contain 
a large amount of Si., believe that this ingredient, up to the amount 
contained in most of the irons we are considering, does not decrease 
the tenacity or ductility of steel. And it is true that good steels are 
made by various processes with as much as 0.20 Si. It is believed 
by the Terrenoire managers that silica is the cause of the bad effects 
usually attributed to silicon. The table of analyses will show that, 
in this case, the ore has not been mistaken for the metal. The slag, 
which contains the silica, has been separately determined. Why 
wrought iron should differ from steel in respect of the effects of Si. 
we have not so far been able to determine, if, indeed, it does so 
differ. It can only be said, with reference to this series of experi- 
ments, that there is an apparent decrease of strength due to an excess 
of this element, while the effects of medium amounts of it are over- 
shadowed by larger causes. The extremes of Si. were, 0.028 and 
0.321. In the best irons it averaged about 0.15. It ran as follows, 
with a regularly decreasing order of value in Tenacity, Si., 0.11, 
0.15, 0.20, 0.10!i 0.16, 0.16, 0.17, 0.14, 0.27, 0.16, 0.07. Reduction 
of Area, Si., 0.07, 0.14, 0.16, 0.14, 0.10, 0.17, 0.16, 0.11, 0.15, 
0.20, 0.16, 0.27. Elongation, Si., 0.10, 0.07, 0.14, 0.17, 0.16, 0.16, 
0.20, 0.11, 0.16, 0.14, 0.15, 0.16, 0.27. 

Effects of Carbon. 
See foregoing remarks on iron B, in which C. is extremely low. 
Iron L, C, averageU35, highest 0.51; P., 0.10; Si., 0.10. Slag 
low. 

Carbon very high ; other impurities quite low. 

Tenacity as bar highest. 

Ductility as bar and link lowest. 

Welding power most imperfect, decreasing as C. increases. 

The following table, from a paper by Wm. Hackney, Esq.,* is 

* Read before the Institution of Civil Engineers, London, April, 1875. 



THE STRENGTH OF WROUGHT IRON. 



9 



valuable in this connection, as showing the amounts of C. in various 
well-known brands of wrought iron and steel : 

PERCENTAGES OF CARBON IN SOME VARIETIES O;^ IRON AND STEEL. 



Series of the Irons. 



Description. 
Soft puddled iron, . 

Armor plates, . . . 

Iron rail. .... 
Lowmoor boiler plate, 
Staffordshire boiler 
plate, 

Kussian bar iron, . 



Swedish iron bar, . . 

Steely puddled iron. 
Iron made b}' Catalan 
process direct from 

the ore, 

Soft puddled steel, . . 
Puddled steel rail, . , 
Hard puddled steel, . . 



Percentage 
of Carbon. 

trace* 

0.0161 

0.033t 

0.044t 

09+ 

0.10+ 

0.191 

0.272t 
0.340t 
0.0541 
0.087t 
0.386t 
0.30 to 0, 

tracesf 
0.420t 

0.50 If 

0.55J 

l.SSOf 



Series of the Steels. 



40j 



Description. 
j Extra soft Fagersta 
I Bessemer steel, 
Extra soft Dowlais 

Bessemer steel, 
Crewe boiler-plate steel, 

Bessemer process, . 
Locomotive crank-axles, 

Seraing Bessemer steel, 
Locomotive crank-axle, 

by Vickers, Sheffield, 
Rails and tires, 
Bessemer spring steel, . 
Crucible steel : 

For masons' tools. 

For chipping chisels, . 

Crank axle (by Krupp) 

Gun (by Krupp), . 

For flat files, . . . 
Forged Indian wootz, . 



Percentage 
of Carbon. 

J0.085§ 

}0.135|I 

1 22 too. 24^ 

/ 0.49 J 

j 0.46* 

0.30 to 0.50 
0.45 to 0.55+ 

0.6* 
0.75* 
, 1.05+ 
l.lSf 
1.20* 
1.6451 



Iron L is, therefore, a so-called puddled steel, or more properly 
a weld-steel. Since its impurities, other than C, are so small, it is 
impossible to avoid the conclusion that C. is the cause of its marked 
physical character. This is more plainly showm by the following : 

H in. bar, C. 045, has 70,000 tension and 6.5 per cent, elongation. 
If in. bar, C. 0.51, has 67,000 tension and 6.5 per cent, elongation. 
C. 0.21 to 0.25 has average 58,000 tension and 13 per cent, elongation. 

Iron K, C, 0.07; P., 0.15; Si., 0.15; slag low. 
C. slightly high; other impurities medium. 
Iron well worked and very uniform. 
Tenacity as bar and link very high. 
Ductility below medium. 
Welding power quite low. 

The ductility was very fair when the bar was not nicked. The 
fracture was fine and silvery, like that of low steel. These facts, and 
the medium amounts of other impurities, point to C. as the harden- 



* A. Willis. 
d D. Forbes. 



t J. Percy 

II Snelus. 



X A. Greiner. 
^ F. W. Webb. 



10 THE STRENGTH OF WROUGHT IRON. 

ing element. Irons having similar amounts of P. and Si., and low 
carbon, like irons A and C, have lower tenacity and higher ductility. 

Iron E, C, 0.018; P., 018; Si., 0.16. 

C. very low; other impurities medium. 

Tenacity below average. 

Ductility high. 

Welding power pretty good. 

These phenomena seem to be connected with low carbon. 

Conelusions about Carbon. — So much is known concerning the 
influence of C. on both wrought iron and steel, that there is little 
danger of falling into error about it. The irons under consideration 
have C. almost exclusively low and pretty uniform; the exceptional 
cases give very marked physical results, especially iron L, which is 
the only one really high in C. The other irons ranged between 
0.015 and 0.07. Carbon ran with the following decreasing order of 
value in Tenacity, C, 0.35, 0.07, 0.042, 0.04, 0.05, 0.04, 0.032, 
0.033, 0.015, 0.02, 0.018, 0.03. Reduction of area, C, 0.02, 0.03, 
0.05, 0.033, 0.018, 0.032, 0.04, 0.04, 0.07, 0.015, 0.04, 0.35. Elon- 
gation, C, 0.05, 0.02, 0.033, 0.03, 0.032, 0.04, 0.04, 0.07, 0.015, 
0.04, 0.35. 

It seems thus easy to vary the physical qualities of puddled iron 
by carbon ; but whether or not it is easy to uniformly vary the 
carbon in puddled iron, the checkered history of the "puddled-steel" 
process will show. As we shall observe farther on, for uses in 
which the value of an iron depends on the strength of the particular 
kind of weld given to these links, C. must be under 0.04. But for 
uses in which the strength of the bar is the measure of fitness, C. 
may run up to 0.50 or more. 

Manganese is so very low in all these irons that its effects cannot 
be traced. It is highest in one lot of iron D, viz., 0.097; but even 
this could have little effect, in view of the fact that Mn. is often three 
times as high in very soft steels, and sometimes runs above one per 
cent, in low structural steels. Mn. seems to toughen steel, and to 
make it cast sound; its hardening effect up to Mn. 0.20 to 0.30 is 
slight. 

Copper is very low in all the irons, except M (Cu. 0.31 to 0.43), 
which has about the average tenacity and ductility. Cu. is next 
highest (Cu. 0.17) in iron A, which has rather low tenacity, but 
very high ductility, on account of its low carbon (C. 0.02). These 
experiments furnish no evidence that copper affects strength. Its 
effect on welding will be farther considered. 



THE STRENGTH OF WROUGHT IRON. 11 

Nickel was only high (Ni. 0.34) in some of the bars of iron M, 
but did not appear to aifect their strength. That it may have 
helped their welding capacity is farther referred to. 

Cobalt was so low (Co. 0.11 maximum) that its effects on strength 
could not be traced. Possibly copper may have been neutralized 
by Ni. and Co. in its effect on strength, but these data are not 
evidence one way or the other. 

Sulphur was extremely low in all the irons, S. 0.046 being the 
highest percentage in one lot of iron M. So little S. did not affect 
welding power, as wq shall observe farther on ; and it could hardly 
impair strength, when irons red-short from much S. are usually 
strong. 

Slag. — This averages about 1 per cent. It is lowest in iron L 
(slag 0.38), and highest in the 2-inch bar of iron N (slag 2.26). 
This bar had 51,700 lbs. tenacity, and 8.7 per cent, elongation ; 
while the 1^ inch bar of iron N, with 1.258 slag, had 56,000 lbs. 
tenacity, and 21.7 per cent, elongation. Was this the result of too 
little work on the larger bar, or of the slag per se f Is the presence 
of much slag merely an indication of too little work — of a loose 
structure resulting from too little condensation of the fibres? Or 
does the slag, as slag, or dirt, exert an independent weakening in- 
fluence ? Referring to the table of analyses we find : 



Iron. 


Size. 


Slag. 


Iron. 


Size. 


Slag. 


L 


¥' 


0.668 








L 


¥' 


0.388 





IF^ 


1.096 


L 


iiV^ 


0.192 





If^^ 


0.974 


L 


W' 


0.326 


p 


1 ^/ 


0.848 


L 


W' 


0.308 


p 


If^^ 


1.214 


L 


^¥' 


0.452 


D 


1 /^ 


0.570 


L 


nr^ 


0.376 


D 


2 /^ 


0.546 



It appears that the smallest and most worked iron often has the 
most slag. It is hence reasonable to conclude that an iron may be 
dirty and yet thoroughly condensed ; and it therefore seems probable 
that the IJ inch bar of iron N was 4300 lbs. stronger than the 
2-inch bar, partly because it had 1 per cent, less slag. The 1-inch 
bar of iron P had nearly 58,000 lbs. tenacity, while the If bar, with 
0.40 more slag, had a little less than 53,000 lbs. tenacity. It is, 
however, impossible to establish any close conclusions from these 
small variations of slag. The investigation requires analyses of 
irons equally worked, some of the specimens being purposely made 
very dirty. 



12 THE STRENGTH OF WROUGHT IRON. 



WELDING. 

Before comparing the irons under this head, it may be well to 
briefly consider the heretofore ascertained facts, and the speculations 
which grow out of them. The generally received theory of Avelding 
is that it is merely pressing the molecules of metal into contact, or 
rather into such proximity as they have in the other parts of the 
bar. Up to this point there can hardly be any difference of opinion, 
but here uncertainty begins. 

What impairs or prevents welding? Is it merely the interpo- 
sition of foreign substances between the molecules of iron, or of iron 
and any other substance which will enter into molecular relations or 
vibrations with iron? Is it merely the mechanical preventing of 
contact between molecules, by the interposition of such substances ? 
This theory is based on such facts as the following: 1. Not only 
iron but steel has been so perfectly united that the seam could not 
be discovered, and that the strength was as great as it was at any 
point, by accurately planing and thoroughly smoothing and cleaning 
the surfaces, binding the two pieces together, subjecting them to a 
welding heat, and pressing them together by a very few hammer 
blows. But when a thin film of oxide of iron was placed between 
similar smooth surfaces, a w^eld could not be effected. 

2. Heterogeneous steel-scrap, having a much larger variation in 
composition than these irons have, when placed in a box composed 
of wrought iron side an(J end pieces laid together, is (on a commer- 
cial scale) heated to the high temperature which the wrought iron 
will stand, and then rolled into bars which are more homogeneous 
than ordinary wrought iron. The w^rought iron box so settles to- 
gether as the heat increases that it nearly excludes the oxidizing 
atmosphere of the furnace, and no film of oxide of iron is interposed 
between the surfaces. At the same time the inclosed and more 
fusible steel is partially melted, so that the impurities are partly 
forced out and partly diffused throughout the mass by the rolling. 

The other theory is that the molecular motions of the" iron are 
changed by the presence of certain impurities, such as copper and 
carbon, in such a manner that wielding cannot occur or is greatly 
impaired. In favor of this theory it may be claimed that, say 2 per 
cent, of copper will almost prevent a weld, while, if the interposition 
theory were true, this copper could only weaken the weld 2 per cent., 
as it could only cover 2 per cent, of the surfaces of the molecules to 
be united. It is also stated that 1 per cent, of carbon greatly im- 



THE STRENGTH OP WROUGHT IRON. 13 

pairs welding power, while the mere interposition of carbon should 
only reduce it 1 per cent. 

On the other hand, it may be claimed that in the perfect welding 
due to the fusion of cast iron, the interposition of 10 or even 20 per 
cent, of impurities, such as carbon, silicon, and copper, does not 
affect the strength of the mass as much as one or two per cent, of 
carbon or copper affects the strength of a weld made at a plastic^ 
instead of a fluid heat. It is also true that high tool steel, contain- 
ing IJ per cent, of carbon, is much stronger throughout its mass, 
all of which has been welded by fusion, than it would be if it had 
less carbon. Hence copper and carbon cannot impair the welding 
power of iron in any greater degree than by their interposition, 
provided the welding has the benefit of that 'perfect mobility which is 
due to fusion. The similar effect of partial fusion of steel in a wrought 
iron box has already been mentioned. The inference is, that im- 
perfect welding is not the result of a change in molecular motions, 
due to impurities, but of imperfect mobility of the mass — of not 
giving the molecules a chance to get together. 

Should it be suggested that the temperature of fusion, as com- 
pared with that of plasticity, may so change chemical affinities as to 
account for the different degrees of welding power, it may be answered 
that the temperature of fusion in one kind of iron is lower than that 
of plasticity in another, and that as the welding and melting points 
of iron are largely due to the carbon they contain, such an impurity 
as copper, for instance, ought, on this theory, to impair welding in 
some cases and not to affect it in others. This will be farther re- 
ferred to. 

The next inference would be that by increasing temperature we 
chiefly improve the quality of welding. If temperature is increased 
to fusion, welding is practically perfect; if to plasticity and mobility 
of surfaces, welding should be nearly perfect. 

Then how does it sometimes occur that the more irons are heated 
the worse they weld ? * 

1. Not by reason of mere temperature ; for a heat almost to dis- 
sociation will fuse wrought iron into a homogeneous mass. 

2. Probably by reason of oxidation, which, in a smith's fire 
especially, necessarily increases as the temperature increases. Even 
in a gas furnace, a very hot flame is usually an oxidizing flame. 
The oxide of iron forms a dividing film between the surfaces to be 
joined ; while the slight interposition of the same oxide, when 
(Jiffused throughout the mass by fusion or partial fusion, hardly 



14 THE STRENGTH OF WROUGHT IRON, 

affects welding. It is true that the contained slag, or the arti- 
ficial flux, become more fluid as the temperature rises, and thus 
tend to wash away the oxide from the surfaces; but inasmuch as 
any iron, with any welding flux, can be oxidized till it scintillates, 
the value of a high heat in liquefying the slag is more than balanced 
by its damage in burning the iron, 

3, But it still remains to be explained why some irons weld at a 
higher temperature than others ; notably, why irons high in carbon 
or in some other impurities can only be welded soundly by ordinary 
processes at low heats. It can only be said that these impurities, as 
far as we are aware, increase the fusibility of iron, and that in an 
oxidizing flame oxidation becomes more excessive as the point of 
fusion approaches. Welding demands a certain condition of plas- 
ticity of surface; if this condition is not reached, welding fails for 
want of contact due to mobility; if it is exceeded, welding fails for 
want of contact due to excessive oxidation. The temperature of 
this certain condition of plasticity varies with all the different 
compositions of irons. Hence, while it may be true that heteroge- 
neous irons, which have diflerent welding- points, cannot be soundly 
welded to one another in an oxidizing flame, it is not yet proved, 
nor is it probable that homogeneous irons cannot be welded together, 
whatever their composition, even in an oxidizing flame. A collateral 
proof of this is, that one smith can weld irons and steels which 
another smith cannot weld at all, by means of a skilful selection of 
fluxes and a nice variation of temperatures. 

To recapitulate. It is certain that perfect welds are made by 
means of perfect contact due to fusion, and that nearly perfect welds 
are made by means of such contact as may be got by partial fusion 
in a non-oxidizing atmosphere or by the mechanical fitting of sur- 
faces, whatever the composition of the iron may be within all known 
limits. While high temperature is thus the first cause of that 
mobility which promotes welding, it is also the cause, in an oxidizing 
atmosphere, of that "burning'^ which injures both the weld and the 
iron. Hence, welding in an oxidizing atmosphere must be done at 
a heat which gives a compromise between imperfect contact due 
to want of mobility on the one hand, and imperfect contact due to 
oxidation on the other hand. This heat varies with each different 
composition of irons. It varies because these compositions change 
the fusing-points of irons, and hence their points of excessive oxida- 
tion. Hence, while ingredients, such as carbon, phosphorus, copper, 
etc., positively do not prevent welding under fusion, or in a non- 



THE STRENGTH OF WROUGHT IRON. 15 

oxidizing atmosphere, it is probable that they impair it in an oxidiz- 
ing atmosphere, not directly, but only by changing the suscepti- 
bility of the iron to oxidation. 

The obvious conclusions are ; 1st. That any wrought iron, of 
whatever ordinary composition, may be welded to itself in an 
oxidizing atmosphere at a certain temperature, which may differ 
very largely from that one which is vaguely known as "a welding 
heat." 2d. That in a non-oxidizing atmosphere, heterogeneous 
irons, however impure, may be soundly welded at indefinitely high 
temperatures. 

These speculations may throw little light on the subject of 
welding. They are introduced for the purpose of indicating the 
direction of farther inquiry and experiment, and of impressing the 
necessity of caution in arriving at conclusions about these irons from 
the limited data afforded by these experiments. 

In reviewing the experiments with reference to welding, and 
under the precaution mentioned, let us observe : 

1st. All the irons were so very low in sulphur that this ingredient 
could not have materially affected welding power. 

2d. As we shall see in detail, farther on, the irregular differences 
in the working and reduction of the bars which affected all other 
physical properties affected this one also. 

Let us first take the singularly impure iron M. Its surfaces were 
pretty well united by welding, but the iron about the weld was 
weakened, especially at a high heat. Of 59 ruptures of links made 
of this iron, 33 were through the weld, and the iron was little 
distorted. Of 303 ruptures of links made of other irons, but 36 
were through the weld. 

The IJ in. bar of iron M presents an exception; it stands high 
on the list in welding capacity, and contains copper 0.31 (average 
Cu. in iron M 0.34). Its phosphorus, slag, and silicon are about 
average. But the bar is also remarkable in containing nickel 0.35 
and cobalt 0.11. Did these ingredients neutralize the copper under 
this special treatment? No other irons contain any notable amount 
of them, except iron A, which has Co. 0.07 and Ni. 0.08 ; but it 
also has Cu. 0.17.* The welds of this iron were very strong, the 
links breaking oftener at the butt than at the weld. 

Two links made from iron M were analyzed from specimens taken 



* This iron may have received the copper while being rolled in a train ordi- 
narily used for copper. 



16 THE STRENGTH OF WROUGHT IRON. 

at the weld end and at the butt end. The weld end had been 
reheated and hammered twice ; the butt end had not been ham- 
mered, and had received heat only by conduction from the other 
end. The analyses show that silicon and slag only were materially 
affected by twice heating and hammering, as follows : 



Iron M, H in. bar, weld end, 
" IJ in. bar, butt end, 
" If in. bar, weld end, 
" 14 in. bar, butt end, 



SI. 


SLAG. 


0.182 


0.994 


0.203 


1.078 


0.177 


1.382 


0.261 


1.738 



In oxidizing to silica, the Si. diffused a small amount of flux, 
which should have helped welding by preventing oxidation or by 
carrying off oxide of iron, or both ; but the amount was so very 
small in this case that its effect cannot be traced. Nor does iron 
J, in which Si. was highest (0.18 to 0.32), confirm this theory. 
Although the other impurities were not high, and the iron was not 
overworked, it welded rather badly. The value of short chains is 
as follows : Best, Si., 0.14, 0.16, 0.07, 0.16, 0.14, 0.17, 0.15, 0.16, 
0.10, 0.16, 0.20, 0.17,0.27. 

Phosphorus, up to the limit of J per cent, had not a notable effect 
on welding. It was lowest in iron 0, w^hich welded soundly; but 
all impurities were low, and welding power was traced to the 
reduction of the bar by direct experiment. The same is true of iron 
P. Omitting one course of piling and hammering largely helped its 
welding power (iron Px). Iron P welded badly, not on account 
of its P. 0.17; for iron B, with P. 0.23, and iron D, with 
P. 0.18, Avelded soundly. Iron M had the highest P., 0.25 (0.21 to 
0.32). While its surfaces stuck together pretty well, the links 
broke through the weld when they were made at a high heat, which 
may be accounted for by the fact that phosphorus increases fluidity, 
and hence capacity for oxidation. The value of short chains is in 
the following order: Best, P., 0.23, 0.18, 0.07, 0.20, 0.18, 0.19, 0.17, 
0.19, 0.17, 0.25, 0.15. 

Carbon notably affected welding. It ran as follows in connec- 
tion with regularly decreasing welding power: C, 0.02, 0.015, 0.04, 
0.03, 0.03, 0.03, 0.04, 0.04, 0.05, 0.032, 0.04, 0.07, 0.35. 

The weld steel, or steely iron, L (C. 0.35), when treated by the 
uniform method usually adopted for chain-cable irons, made the 
worst welds. Iron K, with carbon so low as 0.07, made bad welds, 
although it w^as otherwise a good average chain iron, with a medium 



THE STREN(}TH OF WROUGHT IRON. 17 

amount of impurity. Carbon, in a greater degree than phosphorus, 
promotes fluidity; hence, the iron is "burned'^ at the ordinary 
welding temperatures of low-carbon irons. 

Slag was highest (2.26 per cent.) in the 2 in. bar of iron N, which 
welded less soundly than any other bar of the same iron, and below 
average as compared with the other irons. Slag should theoretically 
improve welding, like any flux, but its eff'ects in these experiments 
could not be definitely traced. 

THE EFFECTS OF REDUCTION FROM PILE TO BAR. 

1st. On Strength. — Early in the course of the mechanical tests, it 
became evident that, although each set of nine bars (1 in., to 2 in. 
diameter) from any maker, was made of the same material and as 
uniformly as ordinary processes would allow, yet there was a notable 
variation in the physical characteristics of the different-sized bars. 
The tenacity, elastic limit, and ductility increased as the diameter 
decreased. In fourteen sets of bars the strength per square inch of 
the 1 in. over the 2 in. ran from 4000 to 7000 lbs.; and in bars 
known to have had uniform treatment, it averaged 5600 lbs. But 
the increase of strength was not uniform. In eight sets of bars the 
strength fell off at the IJ in. size. 

An investigation of the method of manufacture revealed the 
causes of these phenomena. The piles from which the 2 in., IJ in., 
If in., and If in. bars were rolled, had the same cross section, 
diflering only in length. The piles for the IJ in.. If in., 1\ in., 
IJ in., and sometimes the 1 in., were of the same area, although 
smaller than the piles above mentioned. The areas of the piles 
remaining constant with each set, while those of the bars decreased, 
the smaller bars received the most work in the rolls. It was then 
found by numerous experiments that the tenacity and elastic limit 
of tlie various bars of a set increased just in proportion to the decrease 
of the percentage of the area of the bar to that of the pile. 

In order to determine if the converse is true, another set of ex- 
periments was undertaken, and it proved that by preserving a 
uniform proportion of bar to pile, all the bars of the series have 
substantially the same strength per square inch. 

Table V gives two typical examples, selected from the records of 
the Board. That of iron N shows the effect of variation in the per- 
centages of pile to bar; that of iron Fx, the effect of uniformity. (See 
also comparative effects of composition and reduction on page 22.) 



18 



THE STRENGTH OF WROUGHT IRON. 



Table V. 



Iron N, showing 
decrease 


iecrease of strength hy 
of reduction. 


Iron Fx, showing uniformity of i 
strength with uniformity of re- 
^ duction. 




OP 

o 


^ 






.s 






a ^ 


"5) 




a Cw 


"S) 








3J 


^ 




3 


^ 






-_ 


"g 


^ ° 










1c 




■^1 


"m 


;5 


o 




_o 


.2 


ol 


_a^ 


O 


1 


=3" 
So 


a 


1 


i's 




1 


'£ 


^ ■ 


E-i 


W 


<J 


H 


a 


In. 


(Pile 6x4%) 


Lbs. per in. 


Lbs. per in. 


Per cent. 


Lbs. per in. 


Lbs. per in. 


2 


11.36 


51,848 


32,461 


3.92 


50,763 


33,258 


m 


10.22 


54,034 


33,610 


3.45 ■ 


53,361 


35,032 


1% 


8.90 


55,018 


:m,283 


3.34 


53,154 


35,323 


1^ 


7.68 
(Pile 4x3%) 


56.344 


35,889 


3.24 


53,329 


33,520 


i>< 


11.78 


53,550 


34,690 


3.27 


52,819 


34,840 


1^ 


9.90 


54,277 


33,622 


3.53 


52,733 


34,606 


IK 


8.18 


56,478 


33,251 


3.41 


53,248 


33,520 


m 


6.62 


56,543 


32,267 


3.31 


54.645 


34,695 


1 








3.14 


53,915 


36,287 



The falling oif in the strength of the IJ in. bar of iron N is also 
obviously due to the increased percentage of bar to pile. 

The 10 X 10 in. pile designed for the 2 in. bar of iron Fx could 
not be rolled, so that the bar had less reduction and strength than 
the others, which all ran very near the average, viz.: 53,400 lbs. te- 
nacity, and 34,565 lbs. elastic limit. 

It thus appears practicable to manufacture a 2 in. bar in such a 
way that it will sustain 15,000 lbs. more than will a 2 in. bar of the 
same iron manufactured in the ordinary way ; and it is probable that 
a 4 in. bar could be strengthened 60,000 lbs. in a similar manner. 
These facts throw much definite light on the frequent breakage of 
large rolled and hammered bars and forgings. 

But as the use of a special-sized pile for each size of bar would be 
inconvenient and costly/ and would require large additions to rolling- 
mill machinery, the practice is not likely to become common. The 
variation of strength due to that of reduction should, therefore, be 
taken into consideration in all estimates of the strength of structures, 
and in all tables of strength and formulae for the use of wrought 
iron. The report of the Board embraces two tables of the strength 
of bars calculated with this allowance, and also a proof table for 
chain cables, Avhich is quite a different table, and a very much safer 
one, than the standard proof table of the British Admiralty, which 
is now in general use here and elsewhere. 

The Admiralty table assumes that the bars of unequal diameters 



THE STRENGTH OF WROUGHT IRON. 19 

possess equal proportionate strength, and that iron fit for cables has 
the excessively high strength of 60,000 lbs. per inch. The follow- 
ing are typical results selected from many reported by the Board. 
Three cables, five fathoms long, made from IJ in. iron, of good 
quality, were subjected to the Admiralty proof of 91,800 lbs. Three 
similar cables from If in. iron received the 166,500 lbs. proof. The 
usual shop inspection did not reveal any injury; but a magnifying- 
glass showed cracks in the crowns of fourteen links. Eleven 15-fathom 
cables of excellent iron stretched (average) 27 in. under 56 tons pull; 
35 in. under 60 tons. In one cable which 56 tons had stretched 25 
in., 68 tons (only 12 tons more) stretched 56 in., or more than double. 
The Admiralty test for this size is 72 tons. 

The table of the United States Board prescribes what their ex- 
periments have abundantly proved, that the tenacity of the 2 in. bar 
should be between 48,000 lbs. and 52,000 lbs. per sq. in., and that 
the 1 in. bar should have between 53,000 and 57,000 lbs. tenacity. 
Much stronger iron than this makes worse cables, because it does not 
weld soundly, and is not adapted to resist sudden strains. 

2d. Effect of Reduction on Welding. — It is reasonable to suppose 
that in a material consisting of a bundle of fibres, the mobility — the 
flowing capacity — necessary to welding should be greater if the 
fibres are loosely compacted, than if the two surfaces are already 
dense and hard ; although perfectly fitted and cleaned surfaces might 
weld perfectly, however dense. And although we cannot trace the 
effects of slag in these experiments, it is obvious that enough of it 
to protect the surfaces from oxidation and to wash off any oxide 
formed must be advantageous. The least worked iron should con- 
tain the most slag. And the advantage of underworked iron would 
probably be that the slag would lie along the fibres in small threads, 
while in hai:d, and especially in granular iron, it might lie in pockets 
or in masses large enough to seriously affect strength. 

The experiments prove that the strength of the link, which is 
chiefly dependent on welding power, as compared with the strength 
of the bar, was more decreased by overworking than by any other 
cause, excepting the high carbon in the steely iron L, and the ex- 
cess of copper, phosphorus, etc., in the peculiar iron M. The aver- 
age proportion of link to bar in iron Px was 164, while in the 
same iron P, which had received simply another piling and hammer- 
ing, the proportion was but 154.5. 

The proportion of link to bar in iron F was 163.2, while in the 
same iron Fx, which had been much more worked, it was only 154.4. 

The proportion of link to bar in the IJ bar of iron was 184, 



20 THE STRENGTH OF WROUGHT IRON. 

while the proportion in the 1 in. bar of iron was but 148, or 80 
per cent, of the large bar. As iron was very uniform in compo- 
sition, and extremely pure (0., 0.04; P., 0.07 ; Si., 0.07), it is pretty 
certain that this difference in welding power was due to reduction. 

The proportion of link to bar in iron B, the highest on the list, 
was 168.2, while the proportion in iron K, which was next to the 
steely iron L, was 141.6, or 84 per cent, of the highest proportion. 
The difference in the welding powers of irons B and K w^as the re- 
sultant of all causes. 

3d. Effect of Temperature during Reduction. — The strengthening 
effect of cold rolling is well known. One experiment of this series 
strikingly illustrated the difference of strength arising from mere 
underheating as compared with slight overheating. A If in. bar of 
iron F which had 4.12 per cent, of the area of the pile, had 52,537 
lbs. tenacity, and 34,469 lbs. elastic limit, while a 1| in. bar of the 
same iron, which had 4.60 per cent, of the area of the p>ile (not a 
very different reduction from the other bar), had but 49,061 lbs. 
tenacity, and 23,200 lbs. elastic limit. These differences were due 
to the 1| in. bar being underheated and consequently rolled a little 
" cold,'^ while the 1| in. bar was a little overheated, but not ^' burnt.'' 
Such differences were constantly occurring during the experiments 
at the mills. 

WH.AT IS LEARNED FROM CHEMICAL ANALYSES. 

So far, it may appear that little of use to the makers or the users of 
wTought iron has been learned. But it should be remembered, as was 
remarked at the beginning of the paper, that all these irons were 
intended to be as nearly as possible alike, and to be adapted to the 
peculiar use of chain-cable. The makers generally understood the 
necessary conditions, and every effort was made to reach this special 
standard of excellence. Had it been reached, the irons would have 
all been exactly alike in physical character, and presumably simi- 
lar, although not necessarily alike in chemical character, for certain 
ingredients may replace others within limits which are perhaps nar- 
row. Certainly, the attempt to make all the irons conform to a well- 
known standard of quality was the worst possible way to ascertain 
the distinctive effects of the various altering ingredients. In order 
to make this latter determination, one series of irons should have 
been made as uniform as possible in all ingredients except one, for 
instance, phosphorus, and that one should have been varied as much 
as possible. Another sei-ies should have been alike except in Silicon, 
and so on, through the list of altering ingredients. The series of 



THE STRENGTH OP AVROTTGHT IRON. 21 

tests which the Board has undertaken on steels was devised upon 
this principle. It was, however, thought best, after the physical 
tests of these irons were completed, to subject them to analysis, in 
the hope that some good result .would follow. This hope has been 
realized in an unexpected and somewhat surprising manner. 

1st. The want of uniformity in the chemical composition of the 
same brand of iron is a conspicuous defect which is readily accounted 
for. In iron M, silicon varied from 0.16 to 0,26; in iron J, it 
varied from 0.18 to 0.32. In iron P (which had the best average 
qualities), phosphorus varied from 0.09 to 0.25 ; in iron D it varied 
from 0.12 to 0.24, and in iron J from 0.14 to 0.29. 

Starting with a uniform pig iron, the puddling process may or 
may not remove a large amount of silicon, phosphorus and carbon, 
according to the temperature and agitation of the bath, the "fix'' 
used in the furnace, and from many causes under the puddler's con- 
trol, and dependent on his knowledge and skill. 

Such variations would be entirely inadmissible in the most com- 
mon grades of steel; in fact, they could not occur in the cheap steel 
processes, when using a uniform pig iron, except by a special eflPort. 
In the Bessemer process, the completion of the oxidation of silicon 
and carbon is obvious to the inexpert observer ; in the open-hearth 
process, unmistakable tests are taken during the operation. The 
character of steel can be surely predicated on the analysis of its 
materials; that of wrought iron is altered by subtle and unobserved 
causes. Should it be urged in favor of wrought iron, that P. can 
be largely removed during its manufacture, while in the steel man- 
ufacture it cannot be, it may be answered that there is an abundance 
of pig irons which do not contain much P. ; and it is better to be 
sure of a definite amount of a deleterious ingredient than to run the 
risk of a variable amount. 

We are not prepared to show the exact effect of varying reduction 
on steel. Ingots of the same grade of steel, from 6 in. square to 14 
in. square, are employed for the same sized bars ; the larger ones 
are preferred, notwithstanding the greater cost of working them, 
not because small ingots will not make good bars, but because they 
make too much scrap. Steel depends comparatively slightly on 
condensation for its density, but very greatly on its being cast from 
a fluid state. It is a crystalline mass in both large and small 
ingots, and not a bundle of fibres of iron more or less compacted. 

2d. This matter of varying strength due to varying reduction — 
the most important developed by the series of experiments — is made 
all the more certain and useful by the analyses; for without a 



22 THE STRENGTH OF WROUGHT IRON. 

knowledge of the composition of the bars and of the specific effects 
of different ingredients, a part of the variation now traced to re- 
duction might have been attributed to composition. 

It may be stated in general terms that notwithstanding this 
attempt at uniformity, the differences in reduction in the rolling mill, 
from pilti to bar, caused as much variation in the physical qualities 
of these irons as did the differences in the chemical composition of the 
whole series of irons, excepting the steely iron L. The highest differ- 
ence in tenacity, due apparently to varying reductions, is 9969 lbs. 
per square inch. The highest difference between the average ten- 
sional resistances of all the irons (excepting the steely iron L), due 
to all causes, is but 7109 lbs. The following illustrations are more 
in detail (see, also, foregoing Table V) : 

IKON p. 

Per sq. in. 

Tenacity of 1 in. bar (1.74 per cent, of pile) above 2 in. (6.98 per cent, of pile), . . 7,935 lbs. 
Elastic limit " " " " " " . . 7,352 lbs. 

IRON F.— 2d Lot. 

Tenacity of li/g in. bar (2.76 per cent, of pile) over 2 in. (5.23 per cent, of pile), . . 4,698 lbs. 
Elastic limit " " " *' " " . . 3,227 lbs. 

IRON F.— 3d Lot. 

Tenacity of % in. bar (1.60 per cent, of pile) over V/^ in. (6.13 per cent, of pile), . . 9,656 lbs. 

% " (3.68 per cent, of pile) over 4 in. (15.70 per cent, of pile), . . 7,786 lbs. 

Elastic limit of % in. bar " " " " " . . ^ 15,045 lbs. 

Tenacity pf 1 in. bar (3.14 per cent, of pile), " " " . . 5,599 lbs. 

IRON N. 
Tenacity of \}4, in. bar (6.62 per cent, of pile) above 2 in. (11.36 per cent, of pile), . 4,695 lbs. 

IRON A. 
Tenacity of 1 in. bar (3.14 per cent, of pile) over 2 in. (8.72 per cent, of pile), . . 3,575 lbs. 

IRON D. 

Difference in phosphorus in 1 in. and 2 in. bars, 0.05 ; other ingredients about alike. 

Tenacity of 1 in. bar over 2 in. bar, 9,969 lbs. 

The following are apparently results of composition : 

COMPARATIVE TENACITY. 

Of iron highest in average qualities over the one lowest in impurities, . . . . 3,229 lbs. 

Of most tenacious steely iron (carbon 0.28) over least tenacious (carbon 0.03), . . 15,464 lbs. 

Of an iron with phosphorus 0.25, over same iron with phosphorus 0.09, . . . 4,963 lbs. 

3d. The variation of welding power by reduction, in a greater 
degree than by composition, has already been shown in detail. 
Chemical analyses were necessary to establish this fact. 

4th. To the steel maker and user it will appear somewhat re- 
markable that phosphorus may run up to nearly a quarter of one 
per cent., with carbon 0.03 and silicon 0.15, in the best chain cable 



THE STRENGTH OF WROUGHT IROX. 23 

irons, when it is considered that low tenacity and high ductility are 
the essential features of such irons, and that the effect of this ingre- 
dient is to produce exactly opposite results. 

5th. The comparison of chemical and physical results suggests a 
number of experiments which w^ould go far to settle vexed questions 
^and improve the practice, especially with regard to welding. 

(1.) Regarding slag, it has been shown that a larger amount is 
sometimes found in a well-worked than in a less reduced iron, and 
that its effects are uncertain. Experiments should be arranged to 
show what composition of slags will readily come out of the pile in 
rolling; whether 2-high or 3-high trains will best remove them, 
and how much and what kind of slag affects strength and welding. 
A stable oxide of iron, which would probably do the most harm, 
could be formed by blowing superheated steam upon red-hot bars 
before piling. It might be proved that v^ery fusible slags, or fluxes, 
should be placed in the pile to protect surfaces from oxidation and 
to wash away less fusible impurities. 

(2.) It has already been suggested that special irons, having 
respectively a certain ingredient in excess and the others low and 
uniform, should be made, in order to ascertain, in a conspicuous 
manner, the physical effects of the various ingredients. 

(3.) deferring to a previous recapitulation of remarks on weld- 
ing : The effects of very different temperatures on irons varying in 
composition, as compared with that uniformly high temperature 
usually known as a ^' welding heat," should be much more carefully 
ascertained. And the effects, and more especially the means of 
welding in a non-oxidizing flame, where mobility of surfaces can 
be got without ^^ burning," should be made the subject of elaborate 
experiments. The excellent welding of a heterogeneous mass of 
steel and iron, protected from oxidation by being placed in an iron 
box which will stand a high heat, has been referred to. The system 
of gas-welding by which Mr. Bertram welded boilers, at Woolwich, 
twenty years ago, has since been in regular use by the Butterly Com- 
pany, in England, for joining the members of wrought iron beams 
of large section. It should seem within the power of modern engi- 
neering and chemistry to provide means for the perfection in a non- 
oxidizing atmosphere, of welds, like those of ships' cables and bridge 
links, upon which hang so many lives and so much treasure. 

CONCLUSIONS. 

I. Although most of the irons under consideration are much alike 
in composition, the hardening effects of phosphorus and silicon can 



LIBRARY OF CONGRESS | 

019 422 848 A 



24 THE STRENGTH OF WROUGHT IRON. 

be traced, and that of carbon is very obvious. Phosphorus up to 
0.20 per cent, does not harm and probably improves irons contain- 
ing silicon not above 0.15, and carbon not above 0.03. None of the 
ingredients, except carbon, in the proportions present, seem to very 
notably affect welding by ordinary methods. 

II. The strength of wrought iron and its welding power by ordi- 
nary methods are varied as much by the amount of its reduction 
in rolling as by its ordinary differences in composition. Uniform 
strength may be promoted by uniform reduction, but only at such 
increased cost of manufacture that the practice is not likely to 
obtain. Therefore, the reduced strength of large bars made by 
ordinary methods should be considered in designing machinery and 
structures. 

III. In accordance with these facts, the United States Test Board 
has shown, by trial, the unsafety of the Admiralty proof tables for 
chain-cable, and has prepared new ones, and also new tables of the 
strength of different sized bars. The Board has demonstrated that 
the tenacity of 2 in. bar for chain cable should be between 18,000 
and 52,000 lbs. per square inch, and of 1 in. bar between 53,000 
and 57,000 lbs., and that stronger irons than these make worse cables 
because they have low ductility and welding power. 

IV. Chemical analyses, made in connection with physical tests, 
are indispensable to conclusions about either the character or treat- 
ment of iron. In this series of experiments the demonstration that 
strength is dependent on reduction is made more definite and useful 
by the analyses. 

V. Analyses also prove that the same brand of wrought iron may 
be heterogeneoLis in composition, and they emphasize the previously 
known fact that wrought iron making processes as compared with 
the cMB^)\steel processes necessarily give an uncertain character to 
the former material, while to the latter the desired quality may be 
imparted with certainty and uniformity. 

VI. The ordinary practice of welding is capable of radical im- 
provement ; the fact has been fully demonstrated ; the means should 
be made the subject of complete experiments. The perfection of 
means for welding in a non-oxidizing atmosphere would seem to be 
the promising direction of improvement. 

The elaborate mechanical tests made by Commander Beardslee 
have developed or confirmed other very important principles re- 
garding the use of wrought iron, which this paper, alread}^ too 
long, cannot properly consider. They will appear in detail in the 
reports of the United States Test Board. 



TAM70 
-HIS 



LIBRARY OF CONGRESS 



019 422 848 P ^ 



